At least 6 million people worldwide require long-term or permanent confinement to wheelchairs due to lower limb disabilities. Lower limb disabilities may be caused by such conditions as spinal cord injury (SCI), traumatic brain injury (TBI), stroke, cerebral palsy (CP), spina bifida, multiple sclerosis (MS), and others. Long-term confinement to a sitting position in a wheelchair may cause or contribute to physiological or psychological deterioration. Such deterioration may result in poor health, poor quality of life, low self-esteem, and high medical expenses. In addition, sitting in a wheelchair may adversely affect or inhibit social interaction with others who are standing.
Wheelchairs have been described that enable a wheelchair user to stand. Various configurations of such described wheelchairs have been described for various purposes. Some enable the wheelchair user to stand during limited motion of the wheelchair. However, such described wheelchairs are optimized for motion when the user is seated. Stable motion of the wheelchair when the wheelchair user is standing may be limited, for example, to relatively slow motion on level surfaces.